Composition of poly(thioamides) and accelerator

ABSTRACT

A combination of a vulcanization accelerator and an inhibitor which allows longer and safer processing time for rubber, the inhibitor being characterized by the nucleus   WHERE N IS 2 TO 4.

Uiteii States Coran et al.

ate

[ COMPOSITION OF POLY(THIOAMIDES) AND ACCELERATOR [75] Inventors: Aubert Yaucher Coran; Joseph Edward Kerwood, both of Akron,

Ohio

[73] Assignee: Monsanto Company, St. Louis, Mo.

[22] Filed: Aug. 2, 1972 [21] Appl. No.: 277,331

Related US. Application Data [52] U.S. Cl. 252/182, 252/402, 260/795 B, 260/780 Jan. 21, 1975 [51] Int. Cl. C08c 11/54, COSd 9/00 [58] Field of Search 252/182, 402; 260/795 R, 260/795 B, 780

[56] References Cilied UNITED STATES PATENTS 12/1970 Coran ..260/79.5 2/1971 Coran ..260/79.5

Primary Examiner-Christopher ,A. Henderson Attorney, Agent, or FirmRichard O. Zerbe [57] ABSTRACT A combination of a vulcanization accelerator and an inhibitor which allows longer and safer processing time for rubber, the inhibitor being characterized by the nucleus where n is 2 to 4.

13 Claims, N0 Drawings COMPOSITION OF POLY(TI-IIOAMIDES) AND ACCELERATOR CROSS REFERENCE TO RELATED APPLICATIONS This application is a division of application Ser. No. 113,633 filed Feb. 8, 1971 now U.S. Pat. No. 3,775,428, issued Nov. 27, 1973 and a continuation-inpart of application Ser. No. 80,815 filed Oct. 14, 1970 now abandoned. Ser. No. 1 13,633 is a continuation-inpart of application Ser. No. 704,186 filed Sept. 20, 1967, now abandoned, which is a division of application Ser. No. 646,202 filed June 15, 1967, now abandoned which is a continuation-in-part of the copending application Ser. No. 579,493 filed Sept. 15, 1966, now abandoned, a continuation-in-part of the copending ap plication Ser. No. 549,730 filed May 12, 1966, now abandoned, and a continuation-in-part of the copending application Ser. No. 459,466 filed May 27, 1965, now abandoned. Said Ser. No. 80,815 filed Oct. 14, 1970 is a division of said Ser. No. 704,186 filed Sept. 20, 1967. The aforesaid prior applications are incorporated herein by reference.

BACKGROUND OF THE INVENTION The invention pertains to the field of controlledrubber vulcanization art. The applicable U.S. patent classification defines the invention as retarders.

In the manufacture of vulcanized rubber products, crude rubber is combined with various other ingredients such as fillers, accelerators, and antidegradants to alter and improve processing of the rubber and to improve the properties of the final product. The crude rubber is put through several steps in the plant before it is ready for the final step of vulcanization. Generally, the rubber is mixed with carbon black and other ingredients except the vulcanizing agent and accelerator. Then the vulcanizing and accelerating agents are added to this masterbatch in a Banbury mixer or a mill. Scorching, viz., premature vulcanization, can occur at this stage of the processing, during the storage period before vulcanizing, and during the actual vulcanization. After the vulcanizing and accelerating agents are added, the mixture of crude rubber is ready for calendering or extruding and vulcanization. If premature vulcanization occurs during the storage of the crude mixtures or during processing prior to vulcanization, the processing operations cannot be carried out because the scorched rubber is rough and lumpy, consequently, useless. Premature vulcanization is a major problem in the rubber industry and must be prevented in order to allow the rubber mix to be preformed and shaped before it is cured or vulcanized.

There are several reasons offered for premature vulcanization. The discovery of the thiazolesulfenamide accelerators constituted a major breakthrough in the vulcanization art, because thiazolesulfenamides delayed onset of the vulcanizing process; but, once it started, the built-in amine activation of the thiazole resulted in strong, rapid curing. Mercaptobenzothiazole is a valuable organic vulcanization accelerator but by present strandards would be considered scorchy. It has been largely replaced by the delayed-action accelerators. The developement of high pH furnace blacks which lack the inherent inhibiting effect of the acidic channel blacks and popularity of certain phenylenediamine antidegradants which promote scorching have placed increasingly strigent demands on the accelerator system.

Retarders have long been available to rubber compounders. These include N-nitrosodiphenylamine, salicylic acid, and a terpene-resin acid blend. See Editors of Rubber World, Compounding Ingredients for Rubber," -128(3rd. Ed., 1965). Acids as retarders are generally ineffective with thiazolesulfenamide accelerators or adversely affect this vulcanizing process. Ni trosoamines as retarders are only of limited effectiveness with thiazolesulfenamides derived from primary amines.

SUMMARY We have discovered a class of sulfenimides which are extremely valuable inhibitors of premature vulcanization. The characteristic nucleus is where the dangling valence on the nitrogen is linked to a second carbonyl and R is alkyl, aryl, or cycloalkyl. Aryl is used in the usual generic sense to mean any univalent organic radical where free valence belongs to an aromatic carbocylic nucleus and not to a side chain. The term includes radicals substituted in the carbocyclic nucleus, for example, by alkyl, alkoxy, nitro, chloro, bromo, fluoro, iodo, and hydroxy. Alkyl is used in the usual generic sense to mean univalent aliphatic radicals of the series C,,H Primary, secondary, and teritary alkyls are included, for example, straight or branched chains. The term cycloalkyl includes cycloalkyl radicals of 5 to 8 carbon atoms in the ring. The R may be substituted to give a bis-sulfenimide of the formula R'S-RS-R'where R is an alkane, arylene, or cycloalkane and R is an imide. A combination of an accelerator and an inhibitor of this invention is an improved rubber additive which allows longer and safer processing time.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Our invention is that bis-sulfenimides having the formula l,4-bis( 2-thiosuccinimido)butane l,3-bis(2-thiosuccinimido)-3-isobutane, and

1,5 -bis( 2-thiosuccinimido)pentane.

Rubber stocks containing delayed action accelerators can be used in the process of this invention. Cheaper, more scorchy accelerators can also be used with an excellent degree of improvement. The improved vulcanizing process of this invention can be used advantageously to process stocks containing furnace blacks as well as stocks containing other types of blacks and fillers used in rubber compounding. The invention is also applicable to gum stocks.

Our invention is applicable to rubber mixes containing sulfurvulcanizing agents, organic accelerators for vulcanization, and antidegradants. For the purposes of this invention, sulfur-vulcanizing agent means elemental sulfur or sulfur-containing vulcanizing agent, for example, an amine disulfide or a polymeric polysulfide. The invention is applicable to vulcanization accelerators of various classes. For example, rubber mixes containing the aromatic thiazole accelerators which include benzothiazyl-2-monocyclohexyl sulfenamide, Z-mercaptobenzothiazole, N-tert-butyl-2- benzothiazole sulfenamide, 2-benzothiazolyl diethyldithiocarbamate, and 2-(morpholinothio)benzothiazole can be used. Amine salts of mercaptobenzothiazole accelerators, for example, the t-butyl amine salt of mercaptobenzothiazole, like salts of morpholine and 2,6- dimethyl morpholine, can be used in the invention. Thiazole accelerators other than aromatic can be used. Stocks containing accelerators, for example, the tetramethyl-thiuram disulfide, tetramethylthiuram monosulfide, aldehyde amine condensation products, thiocarbamylsulfenamides, thioureas, xanthates, and guanidine derivatives, are substantially improved using the process of our invention. Examples of thiocarbamylsulfenamide accelerators are shown in US. Pat. Nos. 2,381,392, Smith assigned to Firestone; 2,388,236, Cooper assigned to Monsanto; 2,424,921, Smith assigned to Firestone; and British Pat. No. 880,912, Dadson assigned to Imperial Chemical Indus tries Limited. The invention is applicable to accelerator mixtures. The invention is applicable to stocks containing amine antidegradants. Rubber mixes containing antidegradants, for example, N-l,3-dimethylbutyl-N'- phenyl-p-phenylenediamine, N,N'-bis( 1,4-dimethylpentyl)p-phenylenediamine, and other phenylenediamines, ketone, ether, and hydroxy antidegradants and mixtures thereof, are substantially improved using the process of our invention. Mixtures of antidegradants, for example, a mixture of N-l,3-dimethylbutyl-N'-phenyl-p-phenylenediamine and N,N -bis(1,4- dimethylpentyl)-p-phenylenediamine, furnish a much improved final product when used with the inhibitors of this invention.

The inhibitors of our invention can be used in natural and synthetic rubbers and mixtures thereof. Synthetic rubbers that can be improved by the process of this invention include cis-4-polybutadiene, butyl rubber, ethylene-propylene terpolymers, polymers of L3- butadiene, for example 1,3-butadiene itself or isoprene, copolymers of 1,3-butadiene with other monomers, for example styrene, acrylonitrile, and isobutylenc, and methyl methacrylate. The invention relates to diene relates to diene rubbers, and the terms rubber and diene rubber are synonymous for the purpose of this invention.

Extended Summary of the Invention Compounds containing the characteristic nucleus include other valuable compounds besides those in which the dangling valence on the nitrogen is linked to a second carbonyl. The invention also pertains to compounds wherein said valence is linked to alkyl, aryl, cycloalkyl, hydrogen, alkylene carbon or arylene carbon. The second valence of an alkylene radical may directly satisfy the dangling valence on the carbonyl but an arylene radical is usually linked indirectly to the carbonyl, for example through nitrogen, oxygen, sulfur or an alkylene bridge. Moreover, R may be tri or tetravalent as well as divalent so that the new compounds may in general be represented by the formula (P R(s-N-c-) where n is 2, 3 or 4 and R is the bridging moiety which is preferably hydrocarbon. However, where R is alkylene the chain may be interrupted by oxygen or sulfur. Similarly, where the bridging moiety comprises more than one arylene, the arylenes may be joined by oxygen or sulfur and such equivalents will be understood to be included by alkylene and arylene. llt will also be understood that arylene includes radicals substituted by lower alkyl and lower alkoxy of l to 5 carbon atoms, nitro or chlorine. Illustrative of R where n is 2 are divalent radicals derived by removal of two hydrogen atoms from methane, propane, cyclohexane, isopropane, butane, isobutane, pentane, hexane, heptane, octane, benzene, toluene, diphenyl or from each methyl of xylene (phenylenedimethylene) herein regarded as alkylene. Tri and tetravalent bridging moieties are conve niently derived from esters of mercapto lower fatty acids and di, tri or tetrahydric alcohol. The number of carbon atoms in R is essentially a matter of choice and R may comprise at least 1-24 carbon atoms.

The compounds are conveniently derived from intermediates containing the nucleus Where the dangling valences are satisfied by the same radical, the intermediates are of course cyclic. Thus, the invention comprises compounds of the formula wherein \N- is a radical derived by removal of hydrogen from an imide of a dicarboxylic acid, from a monocarbonyl cyclic urea, from an imide in which nitrogen is linked to carbonyl by alkylene and from a monocarbonyl azole containing one other different hetero atom in the ring. Representative examples are phthalimido succinimido adipimido glutarimido 3,3-dimethylglutarimido hexahydrophthalimido 7-oxabicyclo[2.2. l]heptane-2,3-dicarboximido 7-oxabicyclo[2.2. l ]hept--ene-2,3-dicarboximido tetrapropenylsuccinimido methylsuccinimido octadecylsuccinimido n-decenylsuccinimido 1,4,5 ,6,7,7-hexachlorobicyclo[2.2.1 ]hep-5-ene-2,3-

dicarboximido 5,5-dimethyl-3-hydantoinyl hydantoinyl 5,5-diphenyl-3-hydantoinyl maleimido 4-cyclohexene-1,2-dicarboximido 2-benzimidazolinon-l-yl Z-benzothiazolinon-N-yl 3-arylthio-2-benzimidazolinon-l-yl 3-alkythio-2-benzimidazolinon-l-yl 3-cycloalkylthio-2-benzimidazolinon-l-yl 2-imidazolinon-l-yl 3-cycloalkylthio-Z-imidazolinon-1-yl 3-arylthio-2-imidazolinon-1-yl 3 -alkylthio-Z-imidazolinonl -yl Z-imidazolidinon-l-yl 3-cycloalkylthio-2-imidazolidinon-l-y] 3-ary|thio-2-imidazolidinon-l-yl 3-alkylthio-Z-imidazolidinon-1-yl bicyclo[2.2. l ]hept-S-ene-2,3-dicarboximido alkylbicyclo[2.2.1 ]hept-5-ene-2,3-dicarboximido N-(arylthio)-l ,2,4,5-benzenetetracarboxylic-1,214,5-

diimido N-(cycl0alkylthio)-l ,2,4,5-benzenetetracarboxylicl,2:4,5-diimido N-(alkylthio)-l ,2,4,5-benzenetetracarboxylic- 1,214,5-diimido naphthalimido 3 ,4,5 ,6-tetrahalophthalim ido cyclobutane-l ,2-dicarboximido citraconimido glutaconimido caronimido camphorimido hydrochelidonimido, and diphenimido. Where the aforesaid radical is derived from an imide in which nitrogen is linked to carbonyl by alkylene,

octahydroazoninone, 2-azacycloundecanone and 2- azacyclododecanone.

A sub-class of the new compounds derived from acyclic intermediates is represented by the formula where R is the same di, tri or tetravalent moiety as before, n is the valence of R, Y is hydrogen, lower alkyl, aryl or cycloalkyl. Lower alkyl radicals contain l5 carbon atoms in the chain which may be optionally substituted by phenyl. Examples of lower alkyl are methyl, ethyl, propyl, isopropyl, butyl, amyl, benzyl and phenethyl. Examples of aryl are phenyl, tolyl, ethylphenyl and xylyl. Examples of cycloalkyl are cyclopentyl, cy clohexyl, cyclooctyl and methylcylohexyl. The moiety constitutes a radical, for example, N-(arylthio)carbanioyl, N-(cycloalkylthio)carbamoyl, N(alkylthio)carbamoyl, N-arylcarbamoyl.

More particularly, representative examples of are N-(phenylthio)carbamoyl N-(chlorophenylthio)carbamoyl N-(benzylthio)carbamoyl N-(tolythio)carbamoyl N-(methylthio)carbamoyl N-(ethylthio)carbamoyl N-(propylthio)carbamoyl N-(isopropylthio)carbamoyl N-(t-butylthio)carbamoyl N-(dodecylthio)carbamoyl N-(cyclopentylthio)carbamoyl N-(cyclohexylthio)carbamoyl N-(cyclooctylthio)carbamoyl N-phenylcarbamoyl N-methylcarbamoyl N-ethylcarbamoyl N-propylcarbamoyl N-isopropylcarbamoyl N-t-butylcarbamoyl N-trichloromethylcarbamoyl N-benzylcarbamoyl N-nitrophenylcarbamoyl N-chlorophenylcarbamoyl N-tolylcarbamoyl N-dodecylcarbamoyl N-cyclopentylcarbamoyl N-cyclohexylcarbamoyl, and N-cyclooctylcarbamoyl A third sub-class is represented by the formula where Y, R and n have the same meaning as before n is one or 2 and n" is or 1, the sum ofn' and n" being two and X is alkyl, cycloalkyl or arylr Representative examples of are acetyl, benzoyl, toluoyl, diacety], propionyl, butyrl and valeryl.

Intermediates and Preparation of the Compounds The compounds of this invention are prepared according to the following equations:

R(-SH) 1161 R(-SC1) (3 acid I 9 t- -N-C-) R(SN-C-) acceptor When preparing compounds wherein n is 3 or 4, trithiols or tetrathiols are used as intermediates, examples of which are: 1,2,3-propanetrithiol, 1,2,3-benzenetrithiol, 1,3,5-benzenetrithiol, l,2,3,4rbutanetetrathiol, neopentanetetrathiol, trimethylolethanetri(3-mercaptopropionate), CH C(CH OOCCH CH -SH) trimethylolethanetrithioglycolate, CH C(CH OOCCH -SH) trimethylolpr0panetri(3-mercaptopropionate), CH CH C(CH OOCCH CH -SH) trimethylolpropanetrithioglycolate, CH CH C(CH OOCCH -SH) pentaerythritol tetra(3-mercaptopropionate), C(CH OOCCH CH -SH) and pentaerytritol tetrathioglycolate, C(CH OOCCH -SH) Examples of dithiol reactants suitable as intermediates in the above equation are:

1,1-methanedithiol 1,2-ethanedithiol phenyl 1,2-ethanedithiol 1,3-propanedithiol 1,2-isopropanedithiol 2,2-pr0panedithiol 1,2-propanedithiol 2-sec-butyl-2-methyl-l ,3-propanedithiol l,3-diphenyl-2,2-propanedithiol 1,4-butanedithi0l 2,3-butanedithio] 1,3-isobutanedithiol 1,5-pentanedithiol 1,6-hexanedithiol 1,2-hexanedithiol 2-ethyl-1 ,6-hexanedithiol 2,5-dimethyl-3,4-hexanedithiol 2,5-dimethyl-2,4-hexanedithiol Z-ethyl-l ,3-hexanedithiol 3,5 ,S-trimethyl-l ,1 -hexanedithiol 1,7-heptanedithiol 1,8-octanedithiol 1,2-octanedithiol 2,6-dimethyl-3,7-octanedithiol 10 2,6-dimethyl-2,6-octanedithiol 1,9-nonan edithiol 1,10-decanedithiol 2,2-camphanedithiol 1,11-undecanedithio] 4,8-dithiaundecane-l ,l l-dithiol 1,12-dodecanedithiol 7,8-pentadecanedithiol 1,10-octadecanedithiol 1, l 2-octadecanedithiol 1,18-octadeoanedithiol 12,1 Z-tricosanedithiol 2,2'-oxydiethanethiol 2,2'-thiodiethanethiol 4,4'-oxydibutane-1-thiol 2,2'-( ethylenedithio)diethanethiol,

HSC H SC H SC H SH 1,l-cyclohexanedimethanethiol l,2-cycl0hexanedimethanethiol 1,4-cyclohexanedimethanethiol 4-mercaptocyclohexaneethanethiol 2-mercaptocyclohexaneethanethiol 3-mercaptocyclohexaneethanethiol p-benzenediethanethiol 01,11, p-xylenedithiol 2,5-dimethyl-a, a, p-xylenedithiol a,a'-dimethyl-a, a-xylenedithiol 1,1-cyclopentanedithiol 1,2-cyclopentanedithiol 1,1-cyclohexanedithiol 1,2-cyclohexanedithiol p-menthane-2,9-dithiol 1,1-cycloheptanedithio] Z-methyll l -cyclohexanedithiol 4-tert-butyl-l l -cyclohexanedithi0l 1,1-cyclododecanedithiol l ,1-cyclopentadecanedithiol 9,10-anthracenedimethanethiol o-benzenedithiol m-benzenedithiol 4-ethoxy-o-benzenedithiol S-nitro-m-benzenedithiol 4,5-dimethyl-o-benzenedithiol p-benzenedithiol 4,5-dimethyl-m-benzenedithiol 2,4-dimethyl-m-benzenedithiol 4ethyl-m-benzenedithiol 2,5-dichloro-m-benzenedithiol nitro-p-benzenedithiol 1,4-naphthalenedithiol 1,5-naphthalenedithiol 2,6-naphthalenedithiol 2,7-naphthalenedithiol 1,2,3,4-tetrahydro-2,3-naphthalenedithiol 2,5-toluenedithiol 5-methoxy-2,4-toluenedithiol 3,4-toluenedithiol 2,2-biphenyldithiol 4,4'-biphenyldithiol 4,4'-oxybisbenzenethiol glycol dimercaptoacetate, C l-l lOOCCH SH) and glycol dimercaptopropionate, C H OOCC H -SH) The bis(thioimido)alkanes of this invention derived from imides of dicarboxylic acids are synthesized according to the following equations:

o It 11 /C Et N c t l sci ZH-N c c H II o o The mercaptan is dissolved in n-pentane and then chlorine gas is passed through the resulting solution at -5 to 5C. The orange-yellow sulfenyl chloride is added dropwise to a solution of imide and triethylamine in dimethylformamide. The reaction mixture is allowed to stir for 30 minutes and it is then diluted with water. The product is filtered and recrystallized.

To prepare 1,6-bis(2-thiophthalimido)hexane of the formula grams (0.1 mole) of 1,6-n-hexanedithiol is dissolved in 100 ml. of n-pentane in a 250 ml. round-bottomed three-necked flask equipped with a mechanical stirrer, condenser, a thermometer, and a gas inlet tube. Chlorine gas, 16.0 grams (0.22 mole), is passed through the solution in the flask at -5 to 5C. over a -minute period. The yellow solution of the sulfenyl chloride is added dropwise to a solution of 28 grams (0.2 mole) of phthalimide and 26 grams (0.26 mole) of triethylamine in 150 ml. of dimethylformamide over a period of 30 minutes. The reaction temperature rises 24 to 40C. upon this addition. The reaction mixture is stirred for 30 minutes and then it is diluted with two liters of cold water. The precipitate is filtered and dried. The precipitate weights 37.5 grams which is an 85% yield. Recrystallization of the product gives a white crystalline 1,6- bis(2-thiophthalimido)hexane with a melting point of 171 to 172C. Elemental analysis of the l,6-bis(2-thiophthalimido)hexane shows 6.12% nitrogen and 14.53% sulfur. Calculated percentages for C I-1 M05 are 6.36% nitrogen and 14.55% sulfur.

An 89% yield of 1,6-bis(2thiosuccinimido)hexane is obtained using the synthesis described above. The melting point is 1 18-120C. Elemental analysis of the 1,6-bis(2-thiosuccinimido)hexane shows 7.74% nitrogen and 19.15% sulfur. Calculated percentages for C H N O S are 8.13% nitrogen and 18.61% sulfur.

An 85% yield of 1,4-bis( 2-thiophthalimido)butane is obtained using the synthesis described above. The melting point is 2l02l3C (decomposes).

To prepare 1,2-bis(2-thiosuccinimido)ethane of the formula I o 2 K 2 l N-S-(CH2)2-S-N I CH2 e c CH I 4 n 2 o o 18.8 grams (0.2 mole) of 1,2-ethanedithiol is dissolved in 200 ml. of benzene in a suitable glass reactor. Chlorine gas is passed through the solution at 25c. until the solution clears. The sulfenyl chloride solution is cono c'icentrated by removing 50 ml. of benzene on a rotary evaporator. The sulfenyl chloride solution is added slowly to a solution of 39.6 grams (0.4 mole) of suecinimide and 48.4 grams (0.4 mole) of collidine in 500ml. of benzene over a period of 30 minutes. The precipitate is filtered, washed with water and dried. Recrystallization of the product from dioxane gives substantially pure 1,2-(2-thiosuccinimido)ethane. The melting point is 176-178C (decomposes).

1,2-Ethanesulfenyl chloride (0.] mole) in benzene is added in small portions over a period of one hour to 29.4 grams (0.2 mole) of phthalimide and 30.3 grams (0.3 mole) of triethylamine in 300 ml. of carbon tetrachloride. The mixture is stirred two hours and then added to 600 ml. of water. The precipitate is recovered by filtration and dried. 36 Grams of 1,2-bis(2- thiophthalimido)ethane is obtained. Identification is confirmed by nuclear magnetic resonance spectral analysis.

0.2 Mole of 1,2-ethanesulfenyl chloride is added dropwise to solution of caprolactam( 2- oxohexamethyleneimine) 45.2 g. (0.4 mole) and collidine 48.5 g. (0.4 mole) in 500 ml. of benzene. The solids are collected by filtration and washed with water. 42 Grams of l,2-bis[2(2H)-hexahydroazepinon-lylthio]ethane is recovered. The melting point is ll 81C. recrystallized from toluene-heptane. ldentification is confirmed by nuclear magnetic resonance spectral analysis.

4.28 Grams of chlorine is added at room temperature to 4.7 grams of 3,4-toluenedithiol in 150 ml. of hen zene. The sulfenyl chloride solution is then slowly added to a slurry of 11.2 grams of potassium phthalimide in ml. of dimethylformamide and the mixture stirred for one hour. The reaction mixture is quenched in a liter of water and 3,4-bis(2-thiophthalimido) toluene is recovered by filtration.

The polythiol intermediates used in preparing compounds of this invention may be prepared by hydrolyzing the reaction product of thiourea and the appropriate bromo compound. For example, 1 ,l0-decanedithiol is prepared by adding 100 grams (0.33 mole) of 1,10- dibromodecane to a refluxing solution of 51 grams (0.66 mole) of thiourea in 250 ml. of ethanol. After heating at reflux for 8 hours, a solution of 40 grams sodium hydroxide in 300 ml. of water is added. The solution is heated for two hours during which time an oil layer forms. The oil layer is separated. The alcoholwater solution is acidified with dilute sulfuric acid (7 ml. H SO /50ml. H O) to recover additional quantities of dithiol which is combined with the other portion. The crude dithiol is dissolved in benzene, washed with di lute sulfuric acid and dried over sodium sulfate. The benzene is removed by evaporation to give 63.5 grams of 1,10-decanedithiol, a pale yellow liquid, N 1.500.

To prepare 1,10-bis(2-thiophthalimido)dccane, 20.6 grams (0.1 mole) of 1,10-decanedithiol as prepared above is dissolved in 150 ml. of benzene and 14 grams of chlorine gas is added at room temperature. About 30 ml. of the benzene is removed by vacuum stripping. The sulfenyl chloride solution is added dropwise to a slurry of 35.4 grams of potassium phthalimide in 150 ml. of dimethylformamide while cooling the reaction vessel to keep the temperature below 35C. The reaction mixture is added to one liter of water and the resulting precipitate collected by filtration. 45 Grams of substantially pure, 1,l-bis( 2-thiophthalimido)-decane is recovered, a pale cream colored solid which melts at 13 ll 34C. when recrystallized from toluene. Nuclear magnetic resonance spectral analysis confirms identification of the product.

Compounds of the formula ,cH CH Q Z- CH CH\ omen f CH CH wherein R is phthalimido, succinimido and 5,5-dimethyl-3-hydantoin are prepared as follows.

Dipentene dimercaptan which is believed to be mainly p-menthane-2,9-dithiol is chlorinated to give p--menthane-2,9-sulfenyl chloride. Potassium phthalimide and p-menthane-2,9-sulfenyl chloride are reacted by following substantially the same procedure described above for preparing 1,10-bis-(2-thiophthalimido)decane. Grams of a waxy solid identified as 2,9-bis(2-thiophthalimido)-p-menthane is recovered. p-Menthane-2,9-sulfenyl chloride is reacted with succinimide and triethylamine in dimethylformamide to give 25 grams of a gummy solid identified as 2,9- bis(2-thiosuccinimido)-p-menthane. Similarly, a one molar proportion of 5,5-dimethyl hydantoin is reacted with one molar proportion of p-menthane-2,9-sulfenyl chloride to give a yellow glossy solid identified as 2,9- bis(N-thio-S,5-dimethyl-3-hydantoinyl)-p-menthane.

l,4-Bis(2-thiophthalimido)benzene and l,4-bis(2- thiosuccinimido)- benzene are prepared by reacting pbenzene bis(sulfenyl chloride) with phthalimide or succinimide in the presence of an acid acceptor in an inert solvent and recovering the desired product.

Two molar portions of chlorine are reacted at 0C with one molar portion of 4,4-oxybisbenzenethiol to yield 4,4'-oxybis(benzenesulfenyl chloride). The sulfenyl chloride is then added to two molar portions of naphthalimide and triethylamine in dimethyl formamide at room temperature to give 4,4'-bis(2- thionaphthalimido)oxybenzene. Similarly three molar portions of chlorine are reacted with 1,2,3- propanetrithiol and 1,3,5-benzenetrithiol to give the corresponding sulfenyl chlorides. These sulfenyl chlorides are reacted with phthalimide and succinimide to give respectively. l,2,3-tri( 2-thiophthalimido)propane, l,3 ,5tri(2-thiophthalimido )benzene, l,2,3-tri(2-thiosuccinimido)benzene and 1,3,5tri(2-thiosuccinimido)-benzene.

Neopentanetetrathiol is reacted at about 0C in pentane with four molar portions of chlorine to give the corresponding sulfenyl chloride which is added to potassium hexahydrophthalimide in 200 ml. of benzene. Tetra-(N-thiohexahydrophthalimido)neopentane is recovered.

Similarly, chlorine is added to pentaerythritol tetra(- thioglycolate) in hexane at about 0C. Thee sulfenyl chloride is added to a solution of phthalimide and tri' ethylamine in dimethyl formamide at room temperature. Pentaerythritol tetra(S-phthalimidothioglycolate) of the formula is recovered.

14.2 Grams of chlorine is added to a solution of 24.4 grams of pentaerythritol tetra(3-mercaptopropionatc) in about 300 ml. of benzene. The sulfenyl chloride solu-' 9 /C C C OOCCH CH S-N is recovered.

A solution of n-butyl lithium (0.1 mole) in 40 ml. of hexane is added to a slurry of 19.7 g. of benzanilide in 200 ml. of benzene and 50 ml. of tetrahydroluran at 0C to yield a red-brown solution of N-lithium henzanilide. 0.05 mole of l,2-ethane sulfenyl chloride is added to the N-lithium benzanilide solution at 0C. A white precipitate forms as the sulfenyl chloride is added. The reaction mixture is stirred for two hours after which the precipitate is recovered by filtration, washed with water and dried. 23 Grams of l,2.-bis(N-thio-N-phenyl benzamido)ethane is recovered. The melting point recrystallized from toluene is l54l56C.

A solution of n-butyl lithium (0.1 mole) in 40 ml. of hexane is added to a solution of 13.5 g. (0.1 mole) of N-methyl benzamide in 200 ml. of benzene and 50 ml. of tetrahydrofuran at 0C to yield! a white gummy precipitate of N-lithium-N-methyl benzamide. 0.05 mole of 1,2-ethane sulfenyl chloride is added to a slurry of N-lithium-N-methyl benzamide at 0C. A dark gummy precipitate forms as the sulfenyl chloride is added. The solvent is decanted and the residual solvent removed by evaporation to yield a dark brown oil. The oil is dissolved in hot toluene and the toluene removed by evaporation to give l,2-bis(N-thio-N-methyl benzamido)ethane as a brown tar. Identification is confirmed by nu clear magnetic resonance spectral analysis.

1,2-Ethanesulfenyl chloride (0.l mole) in benzene is added dropwise to 17.2 g. of Z-imidazolidinone and 20 g. of triethylamine in ml. of dimethylformamide at room temperature. After stirring the mixture about one hour, the mixture is quenched in a liter of water to yield a gummy precipitate. the precipitate which melts after drying at l35-l50C is recovered by filtration. The product is l,2-bis(N-thio-2-imidazolidinon-l-yl)cthane mixed with a polymer of the structure Inhibiting Prevulcanization The following table illustrates the invention in greater detail and the best mode for carrying it out, but is not to be construed as to narrow the scope of our in- There are seven stocks in the table and Stock 1 is the control. Stocks 2-7 contain the following concentrations of premature vulcanization inhibitor.

vention. For the rubber stocks tested and described, in- Stock Inhibitor Parts y ight fra, as illustrative of the invention, Mooney scorch 1 times at 121C are determined by means of a Mooney 2 l,6-bis(2-thiophthalimido)hexane 0.22 l st m t 3 l,6-bis(2-thiophthalimido)hexane A4 K4 0 d l l f mmules (t5) requ1red f( )r the 4 l,6-bis(2-thiophthalimido)hexane 0.88 ooney rea mg to use we pomts above the minimum 5 l,4-bis(2-thiophthalimido)butane 0.24 viscosity is recorded. Longer times are indicative of the g i 21 :!ggl" fiz il l g 2 activity of the inhibitor. Longer times on the Mooney 4 t Mm'do) 0'9 TABLE 1 Stock 1 2 3 4 5 0 7 Mooney Scorch at l2lC t 25.3 37.4 47.5 00.8 35. 51.0 04.1; Increase in Scorch Delay 48 88 I40 39 I02 I56 Rheometer at 144C 1 8.0 10.0 12.2 15.0 0.3 11.5 14.0 t, 21.5 22.5 20.3 29.5 22.0 25.2 29.5 R.M.T. 50.2 58.6 00.4 02.0 57.5 511.0 50.0 1t 0.183 0.183 0.173 0.173 0.173 0.1117 0.1113

Scorch Test are desirable because this indicates greater Other prevulcanization inhibitors ofthe invention are processing safety. Percentage increases in scorch delay 25 tested in a similar natural rubber stock containing the are calculated by dividing the Mooney scorch time of same ingredients as previously described except 0.5 the stock containing the premature vulcanization inhibparts N-tert-butyl2-benzothiazolesulfenamide is used itor y the Mooney Scorch time Of the Control Stock, as accelerator in stocks l-5 and 0.6 parts in stock 6 in mu tiply g y 1 a d su st g 00- Th place ofSantocure MOR and 2.0 parts ofsulfuris uscd. creases show the percentage improvemen in s r h The inhibitors are tested at 0.5 parts by weight per 100 delay over the control stock which contains no inhibiparts bb tor. Additionally, curing characterisrics are calculated from the time required to cure the stocks at 144C by means of the Monsanto Oscillating Disk Rheometer Stock i itor which is described by Decker, Wise, and Guerry in h d h l l,2-bis(2-t iosuccinimi 0 et ane Rubber World, December 1962, page 68. From the 2 lHMhhiophthalimidoNew Rheometer data, R.M.T. IS the maximum torque in 3 2,9-bis(Nthio-5,5-dimethyl-3-hydantoinyll-P- Rheometer units, t is the time in minutes for a rise of 9 4 2,9-b1s(2-th1osucc1n1m1do)-p-mcnlh.1nc two Rheometer units above the mmtmum reading of 5 2 9.bi (zqhiophthalimid )-p-menthune the rubber sample, and is the time required to obtain 0 1.2-bist2t2H) y p -y lethunc a torque 90 percent of the maximum.

The trademarks of some compounds used in the TABLE [I practice of this invention are Santocure MOR and Santoflex l3. Santocure MOR is the accelerator 2- Stock 2 3 4 S 6 (morpholmothlo)benzothiazole. Santoflex 13 is the anti-degradant N- l ,3-dimethylbutyl-N-phenyl-pphenylenediamine. gvellgrease 1n Scorch 44 62 40 39 52 I l 3 Table 1 illustrates the results of using l,6-bis(2-thiophthalimido)-hcxane and l,4-bis(2-thiophthalimido)- butane as premature vulcanization inhibitors in stocks Comparable results to those in the above tables illusof natural rubber containing the antidegradant Sant trating utility are obtained with the inhibitors of this inflex l3 and the accelerator Santocure MOR. From the vention which are not illustrated. data of the table it will be noted that 1,6-bis(2-thioph- Concentration studies show that the inhibitors of this thalimido)hexane and l,4-bis(2-thiophthalimido)bu- 55 invention are effective in rubber at concentrations of tane are quite active in the presence of the accelerator 0.05 to 5.0 parts per hundred. Concentrations from as premature vulcanization inhibitors. 0.22 to 3.0 parts per hundred are preferred.

The ingredients for the table are as follows. The Although the invention has been illustrated by typical stocks contain: examples, it is not limited thereto. Changes and modifications of the examples of the invention herein chosen I for purposes of disclosure can be made which do not w constitute departure from the spirit and scope of the Natural rubber 100 invention Carbon black 45 Zinc oxide 3 The embodiments of the mventlon 1n WhlCh an exclu- Stearic acid 2 Hydrocarbon softener 5 sive property or pr1v1lege 1s clalmed are defined as fol Santoflex l3 2 lows- Santocure MOR 1. An accelerator-inhibitor composition conslstmg S fur as fi -fi essentially of a diene rubber organic vulcanization ac- Premature vulcanization inhibitor celerating agent in an amount effective to accelerate vulcanization ofa vulcanizable diene rubber and an inhibitor, in an amount effective to inhibit premature vulcanization of a vulcanizable diene rubber, selected from the group consisting of the formulas:

0 II wherein 1C l \N- is a radical derived by removal of hydrogen from an imide of a dicarboxylic acid, from a monocarbonyl cyclic urea, from an imide in which the nitrogen is linked to carbonyl by alkylene and from a monocarbonyl azole containing one other different hetero atom in the ring, n is 2, 3 or 4 and R contains 1-24 carbon atoms and is alkylene, arylene, cycloalkylene or residue of ester from mercapto lower fatty acid and polyhydric alcohol,

wherein n and R have the same meaning as before, Y is hydrogen, lower alkyl, aryl or cycloalkyl and represents N-(arylthio)-carbamoyl, N-(cycloalkylthio)carbamoyl, N-(alkylthio)carbamoyl, N- arylcarbamoyl, N-alkylcarbamoyl or N-cycloalkylcarbamoyl and is a radical derived by removal of hydrogen from an imide of a dicarboxylic acid which radical has the formula where A is alkylene, cycloalkylene, arylene, alkenylene or cycloalkenylene.

3. A composition of claim 1 in which the inhibitor is of Formula (a) wherein is a radical derived by removal of hydrogen from an imide having the formula 0 an cf m1 x-c 0 where X and Y individually are hydrogen, alkyl, aryl or cyloalkyl.

4. A composition of claim 1 in which the inhibitor is of Formula (a) wherein is a radical derived by removal of hydrogen from an imide in which nitrogen isconnected to carbonyl by al kylene which radical has the formula where A is alkylene hydrocarbon of 3 to 10 carbon atoms.

5. A composition of claim 4 in which n is 2 and R is alkylene, arylene or cycloalkylene.

6. A composition of claim 5 in which A is C H and R is dimethylene.

7. An accelerator-inhibitor composition consisting essentially of a diene rubber organic vulcanization accelerating agent in an amount effective to accelerate vulcanization of a vulcanizable diene rubber and an inhibitor, in an amount effective to inhibit premature vulcanization of a vulcanizable diene rubber, of the f0rmula O Id N-'S- n wherein is selected from the group consisting of phthalimidyl;

hexahydrophthalimidyl, naphthalimidyl, cyclohcxenedicarboximidyl and hexachlor|obicyclo(2.2.l )hcpt- S-ene-dicarbbximidyl, n is 2, 3 or 4, R contains l to 24 carbon atoms and is selected from the group consisting of radical from removing n hydrogens from alkanc, radical from removing n hydrogens from cycloalkane, radical from removing n-l -hydrogens from aryl and radical of the formula carbon atoms and is alkylene, arylene, or cycloalkylene and R is an imido radical.

9. An accelerator-inhibitor combination consisting essentially of a diene rubber organic vulcanization accelerating agent in an amount effective to accelerate vulcanization of a vulcanizable diene rubber and a compound, in an amount effective to inhibit premature vulcanization ofa vulcanizable diene rubber, of the formula R-S-R-S-R wherein R contains 1 to 8 carbon atoms and is alkylene, arylene, or cycloalkylene and R is an imido radical.

10. An accelerator-inhibitor combination according to claim 9 wherein R is phthalimido.

11. An accelerator-inhibitor combination according to claim 9 wherein the accelerator is selected from the group consisting of benzothiazole sulfenamides, thiuram sulfides and thiocarbamylsulfenamides.

12. An accelerator-inhibitor combination according to claim 9 wherein the accelerator is Z-(morpholinothi o)benzothiazole and the inhibitor is l,6-bis(2-thiophthalimido)hexane.

13. An accelerator-inhibitor combination according to claim 9 wherein the accelerator is 2-(morpholinothio)benz0thiazole and the inhibitor is l,4-bis(2-thiophthalimido)hutane. 

2. A composition of claim 1 in which the inhibitor is of Formula (a) wherein
 3. A composition of claim 1 in which the inhibitor is of Formula (a) wherein
 4. A composition of claim 1 in which the inhibitor is of Formula (a) wherein
 5. A composition of claim 4 in which n is 2 and R is alkylene, arylene or cycloalkylene.
 6. A composition of claim 5 in which A is C5H10 and R is dimethylene.
 7. An accelerator-inhibitor composition consisting essentially of a diene rubber organic vulcanization accelerating agent in an amount effective to accelerate vulcanization of a vulcanizable diene rubber and an inhibitor, in an amount effective to inhibit premature vulcanization of a vulcanizable diene rubber, of the formula
 8. An accelerator-inhibitor combination consisting essentially of a diene rubber organic vulcanization accelerating agent in an amount effective to accelerate vulcanization of a vulcanizable diene rubber and a compound, in an amount effective to inhibit premature vulcanization of a vulcanizable diene rubber, of the formula R''-S-R-S-R'' wherein R contains 1 to 24 carbon atoms and is alkylene, arylene, or cycloalkylene and R'' is an imido radical.
 9. An accelerator-inhibitor combination consisting essentially of a diene rubber organic vulcanization accelerating agent in an amount effective to accelerate vulcanization of a vulcanizable diene rubber and a Compound, in an amount effective to inhibit premature vulcanization of a vulcanizable diene rubber, of the formula R''-S-R-S-R'' wherein R contains 1 to 8 carbon atoms and is alkylene, arylene, or cycloalkylene and R'' is an imido radical.
 10. An accelerator-inhibitor combination according to claim 9 wherein R'' is phthalimido.
 11. An accelerator-inhibitor combination according to claim 9 wherein the accelerator is selected from the group consisting of benzothiazole sulfenamides, thiuram sulfides and thiocarbamylsulfenamides.
 12. An accelerator-inhibitor combination according to claim 9 wherein the accelerator is 2-(morpholinothio)benzothiazole and the inhibitor is 1,6-bis(2-thiophthalimido)hexane.
 13. An accelerator-inhibitor combination according to claim 9 wherein the accelerator is 2-(morpholinothio)benzothiazole and the inhibitor is 1,4-bis(2-thiophthalimido)butane. 